Non-return valves are counted as belonging to the state of the art in numerous design variants, and they are applied where a flow is desired in only one direction, in order to hold fluid in a channel system or vessel, or for other purposes.
With water supply systems or pumps, a non-return valve is typically provided on the delivery side of the pump, in order to ensure that the system pressure is held at the delivery side after switching off the pump and fluid does not flow back through the pump. One the other hand, with water supply systems which are operated with centrifugal pumps, but also with other centrifugal pumps if these are to operate in quasi self-priming, it is necessary on the one hand to design these accordingly and on the other had to provide a closable filling opening, in order to ensure that fluid is located in the pump on first starting operation. A closable filling opening is to be provided upstream of the non-return valve in the flow direction, since the non-return valve is to prevent a backflow into the pump.
A known water supply system of this type is marketed by the applicant under the description Grundfos MQ. This design in practise has proven its worth, but however has the designs described above and the disadvantages which these entail. Thus, the non-return valve requires comparatively much effort for its installation and removal. Thereby, it is to be ensured that pressure no longer prevails at the delivery side, in order to avoid an uncontrolled pressure loss on removal of the non-return valve and the danger potential which this always entails.